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void  OSTaskStkChk (OS_TCB       *p_tcb,

                    CPU_STK_SIZE *p_free,

                    CPU_STK_SIZE *p_used,

                    OS_ERR       *p_err)

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File

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Called from

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Code enabled by

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os_task.c

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Task only

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Description

OSTaskStkChk() determines  determines a task’s stack statistics. Specifically, it computes the amount of free stack space, as well as the amount of stack space used by the specified task. This function requires that the task be created with the the OS_TASK_OPT_STK_CHK and  and OS_TASK_OPT_STK_CLR options options.

Stack sizing is accomplished by walking from the bottom of the stack and counting the number of of 0 entries  entries on the stack until a non-zero value is found.

It is possible to not set the the OS_TASK_OPT_STK_CLR when  when creating the task if the startup code clears all RAM, and tasks are not deleted (this reduces the execution time of of OSTaskCreate()).

µC/OS-III’s statistic task calls calls OSTaskStkChk() for  for each task created and stores the results in each task’s task’s OS_TCB so  so your application doesn’t need to call this function if the statistic task is enabled.

Files

os.h/os_task.c

Prototype

Arguments

p_tcb

is a pointer to the TCB of the task where the stack is being checked. A NULL pointer indicates that the user is checking the calling task’s stack.

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If OS_CFG_ARG_CHK_EN is set to 1 in DEF_ENABLED in os_cfg.h: if either p_free or p_used are NULL pointers.

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OS_ERR_TASK_OPT

If OS_OPT_TASK_STK_CHK is was not specififed whencreating when creating the task being checked.

OS_ERR_TASK_STK_CHK_ISR

If OS_CFG_CALLED_FROM_ISR_CHK_EN set to 1 in DEF_ENABLED in os_cfg.h: if calling this function from an ISR.

Returned Value

None

Required Configuration

OS_CFG_TASK_STAT_CHK_EN must be enabled in os_cfg.h. Refer to µC-OS-III Configuration Manual.

Callers

Application.

Notes/Warnings

1. Execution time of this task depends on the size of the task’s stack.
2. The application can determine the total task stack space (in number of CPU_STK elements) by adding the value of *p_free and *p_used. This number should add up to the task’s stack size which is stored in the .StkSize field of the OS_TCB of the task.
3. The

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1. #define CPU_CFG_STK_GROWTH must be declared (typically from os_cpu.h). When this #define is set to CPU_STK_GROWTH_LO_TO_HI, the stack grows from low memory to high memory. When this #define is set to CPU_STK_GROWTH_HI_TO_LO, the stack grows from high memory to low memory.

Example Usage